1. Permanent Magnet Irradiation Experiment in RHIC Tunnel February 24, 2015Stephen Brooks, eRHIC meeting1 Material: NdFeB

2. Five Parameter Data Set Location of material – Control, kickers, dump Time period of irradiation (and dosimetry) – T0 = Start (Feb 18 th ), T1, T2, T3, T4, T5 Material (five NdFeB grades of varying quality) Configuration (C-core, bare block, angled) Probe point for field measurement – Magnet holders have 2, 4 or 12 probe points February 24, 2015Stephen Brooks, eRHIC meeting2

3. Current Status All magnet samples have been assembled, holders 3D printed by George Mahler All initial field measurements were taken Samples placed in the tunnel near 10 o’clock February 24, 2015Stephen Brooks, eRHIC meeting3

4. Materials NameDimensionsManufacturerNotes N35 3"X.75X.5(M) Allstar Magnetics LLC epoxy coated, 80C max temp. N35EHepoxy coated, 200C max temp. VAC 863AP VacuumSchmelze GmbH N32~35 equiv., 180C max temp. VAC 688APN25~28 equiv., 230C max temp. N42.25"X.75X.5(M)magnet4less.comNickel coated, clearance stock February 24, 2015Stephen Brooks, eRHIC meeting4 N42

5. Configurations February 24, 2015Stephen Brooks, eRHIC meeting5

6. Configurations (ctd.) C-core produces ~0.4T (eRHIC field) in 5mm gap Type “A” angled configurations are meant to test opposing field situations – Contained in 3D printed holders with probe points February 24, 2015Stephen Brooks, eRHIC meeting6

7. Field Probe Points Type AType BType C February 24, 2015Stephen Brooks, eRHIC meeting7 1 2 10 11 12 1 2 8 7 6 5 4 39 1 2 3 4 1 2 For N42: Probe sockets designed to fit magnet division’s field probe that is accurate down to 1 Gauss. 228 measurements per time period!

8. Dosimetry and Schedule Kicker location ~0.25Gy/day (Paul Bergh study) – Dump presumably more but no-one has measured Time periods: 2 weeks, 1, 2, 4, 8 months Use TLDs for T1, T2 (limit 2-7Gy) Use DOSE-MAP films from Ashland, calibrated between 2-200Gy for all 5 time periods – Six locations, three per tray, shown on next slide Can change location to AGS if insufficient dose February 24, 2015Stephen Brooks, eRHIC meeting8

9. Dosimeter Layout in Tray February 24, 2015Stephen Brooks, eRHIC meeting9

10. T0 Fields for C-cores February 24, 2015Stephen Brooks, eRHIC meeting10

11. C-core Fields Statistics Material“N” Grade (MGOe) B r spec (T)Average Gap Field (T) Range of Variation of (3) Samples (relative) N35351.17-1.220.39691.03% N35EH351.17-1.220.39262.64% VAC 863AP32~351.17~1.210.39211.52% VAC 688AP25~281.03~1.080.35623.13% N42“42”“1.32”0.39610.07% (shuffling??) February 24, 2015Stephen Brooks, eRHIC meeting11 Range of variation within the gap (between probe points 1,2,3,4) was 0.22% on average.

12. T0 Fields for Bare Blocks February 24, 2015Stephen Brooks, eRHIC meeting12

13. Analytic Field Model Assume constant M (magnetisation) within cuboid, with M = B r /  0 (and M = 0 outside) J bound =  × M = surface currents around block February 24, 2015Stephen Brooks, eRHIC meeting13 Calculate with Biot-Savart law double integral Field for B r =1.000T

14. N35 Control B block (example) February 24, 2015Stephen Brooks, eRHIC meeting14 NB: “bare block” measurements came out less accurately than C-core because of high field gradient

15. Derived B r Values February 24, 2015Stephen Brooks, eRHIC meeting15